Games to work on the SCUMM engine (monkey island et al)_________________The best argument against democracy is a five-minute conversation with the average voter
Great Britain is a republic, with a hereditary president, while the United States is a monarchy with an elective king

While not exactly in Portage they do have Linux ports and need the original CDs before they can be made to do anything useful:

Descent: Freespace
Freespace 2

Also, unless you have a Windows installation to copy the .vp files from (the base ones aren't on the CDs as such, they're built at install time from installshield .CAB files) you need something like the icculus Freespace installer available here:

Flight of the Amazon Queen and Beneath a Steel Sky are both in portage, as queen and bass, I think.

Both of these games manage to fully download all the files they need to play as they've been freely released. I.e. an `emerge bass queen` is all that is needed to play these games, so I don't think they belong on this list.